It is definitively possible to use events in process constraints. Your exception, though, implies that you are using a sliding time window on a fact type that is not declared as an event. In later versions I improved the error handling to raise a compile time error when this is detected, but I guess you are using 5.0.1, where it still throws a runtime exception:
java.lang.ClassCastException: org.drools.common.DefaultFactHandle cannot be
cast to org.drools.common.EventFactHandle
at
org.drools.rule.SlidingTimeWindow.updateNextExpiration(SlidingTimeWindow.java:192)
Can you double check your rules to make sure you are not doing that?
Edson
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Edson Tirelli
JBoss Drools Core Development
JBoss by Red Hat @ www.jboss.com